Self-adjusting stair

ABSTRACT

A self-adjustable stair construction wherein the treads of the stair are supported by spacers between upper and lower stringers in a truss assemblage. This stair readily accommodates all variations in landing construction and stairwell sizes such as vertical and horizontal variance. Both rise and run between the treads are simultaneously adjusted with the adjustments being cumulative over stair flight run while maintaining the treads level. The stair may be prefabricated and is to be assembled from parts, installed during or after building construction, is removable and can be relocated and re-adjusted to the new location. This stair may be fitted with a variety of tread shapes which can be replaced, reversed or new treads substituted. The framework of this invention may be used in a form to cast concrete stairs, it can become an integral part of the reinforcement, or it may be used and removed. The stair performs lilke an on-site variable jig to suit variable field conditions.

United States Patent [1 1 Cox [ SELF-ADJUSTING STAIR Joe Warren Cox, 504 Ranch Rd., Thousand Oaks, Calif. 91360 22 Filed: June 6,1974

21 Appl No.: 476,873

[76] Inventor:

Primary Examiner-Price C. Faw, Jr. Attorney, Agent, or Firm-Jack C. Munro 1 May 27, 1975 [57] ABSTRACT A self-adjustable stair construction wherein the treads of the stair are supported by spacers between upper and lower stringers in a truss assemblage. This stair readily accommodates all variations in landing construction and stairwell sizes such as vertical and horizontal variance. Both rise and run between the treads are simultaneously adjusted with the adjustments being cumulative over stair flight run while maintain ing the treads level. The stair may be prefabricated and is to be assembled from parts, installed during or after building construction, is removable and can be relocated and re-adjusted to the new location. This stair may be fitted with a variety of tread shapes which can be replaced, reversed or new treads substituted. The framework of this invention may be used in a form to cast concrete stairs, it can become an integral part of the reinforcement, or it may be used and removed. The stair performs lilke an on-site variable jig to suit variable field conditions.

12 Claims, 45 Drawing Figures PATENTEUEWZY ms SHZET UlUF 8 PATENTED MAY 2 7 I975 SHEET UZUF 8 PATENTEDHHZ? I975 SHEET DSUF 8 PATENTEDHAY 27 m5 SHEET OSUF 8 SELF-ADJUSTING STAIR BACKGROUND OF THE INVENTION The structure of stairways is dependent on several factors and requires meeting minimum dimensional safety standards of the various building codes. Example: The riser (rise) shall not exceed 7%. inches in commercial buildings or 8 inches in houses and the tread (run) shall not be less than lll inches in commercial buildings or 9 inches in houses. The maximum variations in the rise and run in any one flight is threesixteenths ofan inch. Thus. the codes attempt to regu late accuracy of construction. but recognize that it is nearly impossible to achieve equal variation ofall constructed parts in any one flight. All stairs previously constructed exhibit some defect in trying to achieve this uniform variation.

Previous to this invention. stairs were fabricated from all manner of stock materials such as rolled steel shapes. bent plates. welded metal plates, and various kinds of fasteners of different sizes. These stock materials had to be reworked extensively by operations such as cutting. piecing. fitting and extensive welding in order to produce a custom design.

Stair construction has historically relied on various industry practices for stair rise to run ratio formulas. The best is a matter of opinion among individual designers. As a general rule. the rise should be kept between 6% inches and 7% inches for comfort and safety and then a corresponding run is computed by the designer according to a formula. Trial and error solutions are tried first until no code is violated and comfort is achieved within an acceptable limit. Most commercial stairs are designed with the maximum permissible rise and minimum permissible run to reduce the stairwell size.

The convention of producing stairs is for an architect or other designer to make design drawings. then require by specification that fabrication drawings be made by the installer or fabricator and returned for the designers approval. The approved fabrication draw ings should take account of variable field conditions as much as possible. but this is seldom or never done in practice. Approved fabrication drawings are used for shop fabrication of the stairs. The stair built then becomes a rigid framework for field erection. Unfortunately there invariably are variations in the space pro vided for its installation or erection. Only during installation can the errors of stair design in relation to the stairwell space it is suppose to fit be assessed and corrected. Often. several different trades have to struggle with each other to complete the installation over a long period of time. It is also common for stair risers or treads to be shortened or extended at the landings just to make the stair fit. Sometimes landings have to be field modified because the rigidly constructed stair is too difficult to correct.

Prei ious to this invention. field violations of the code limits where often overlooked or avoided by inspectors because to construct the stair precisely in accordance with the approved drawings was normally just not expected. it is a rare occurrence to have the run and the rise within each stair flight exactly equal or to have one flight match the next flight.

SUMMARY OF THE INVENTION This invention, for the first time. can guarantee no code will be violated and comfort standards will be maintained because it adjusts to either the total run or total rise variation in any one flight and may be used to determine what the stairwell will be from a preengineered schedule. This scheduling feature gives the buyer or designer first a selection of riser heights. then the number oftreads and the resulting total run. or vice versa. in just a few seconds of time.

The structure of this invention is depicted in three embodiments. and will be described by the relative movements of the parts used on one side of the stair since both sides are identical. For purposes of descrip tion the stair framework of the invention will be discussed in relation to horizontal and vertical directions of the stair in its normally installed position.

The first embodiment of this invention has live parts. some of which are repeated to form a whole stair. Two inclined stringer spacers are cross members between an upper and a lower stringer forming a simple parallelogram linkage with pivot points at each of the four corners. Mounted to the stringers are the horizontal tread carriers and the vertical tread spacers, each of which have a slot in only one end. which cooperate through a connecting pin to provide adjustment. Extending through the slot in each tread carrier is a pin. This pin cooperates within the slot in the upper end ofthe verti cal tread spacer which spaces the treads the same distance apart and keeps them parallel to the succeeding tread. The stringers are positioned in a parallel relationship by the inclined stringer spacers and are maintained that way throughout the adjustment. The aforementioned pin of each tread carrier and vertical tread spacer provides the adjusting means of the first em bodiment of this invention. The first embodiment utilizes the geometry of an isosceles linkage.

The second embodiment of this invention differs from the first embodiment in that no inclined stringer spacers are employed and there are slots in the vertical tread spacers. The horizontal tread carrier is endwise reversed so that the slot is at the rear end of the tread which provides for adjustability. The overall result of the second embodiment is that the tread carrier and its supported tread are maintained in the desired horizontal position during the entire range of adjustment. The vertical spacer is not always maintained vertical. but may assume an inclined position during a significant part of the adjustment. becoming vertical only when the rise is adjusted to the maximum. The second embodiment is not an isosceles linkage.

The third embodiment of this invention is basically similar to the second embodiment. but there is no slot in the horizontal tread carrier and instead there is a slot in the vertical tread spacer at the junction of the vertical tread spacer with the horizontal tread carrier of its respective step. The tread carrier is always maintained in the desired horizontal position. but as was the case of the second embodiment. the vertical spacer may as some an inclined position.

All three embodiments have the following in common: The upper stringer and the lower stringer are identical. The holes for the tread connections in the stringers are equally spaced and therefore links may be substituted instead of a stringer cut to a certain length. Therefore, the stair may be extended or reduced and still be re-adjusted. A nonstructural closed riser pan can be added to all three embodiments. The resultant adjustable movement is the same. but the slot or slide means to produce this movement is different. The lateral side of the stair is a truss. The truss components of each embodiment are the stringer. tread carrier and the tread spacer, all of which comprise a linkage. The treads themselves serve to laterally space the sides apart, prevent side sway, and to transfer the same adjustment to each side. Each embodiment has one or more inherent advantages for a particular use that the other two do not have.

Some of the numerous advantages of this invention are as follows: When the rise of the stairway is adjusted. the depth of each tread (run) is automatically adjusted proportionately so that each run is equal. During adjustment, each riser height (rise) is automatically main tained equal throughout the total rise of the stair unit. The stair framework can be adjusted for variations of horizontal and vertical distances between landings. Also, a limited amount of torsional bending of one end of the stairway unit with respect to the opposite end of the stairway unit is possible in order to compensate for any misalignment of the landings with respect to each other. The stair framework is a truss, therefore the stair exhibits a high strength to weight ratio. The stair may be prefabricated in a disassembled or collapsed position and transported to the job site and installed by unskilled labor. It is estimated that the total cost of the stairs installed with this invention will be substantially less than the cost of the prior art stairs. The different parts making up the stair framework can be reversed with the result that each embodiment will still operate in the same manner. Each embodiment of this invention can assume an infinite number of separate adjustable positions within each range of adjustment. Automatically during adjustment, the rise to run relationship follows industry accepted proportional rules. In other words, as the rise decreases, the run increases and vice versa. If desired, balusters and handrails may be integrally attached to each stair because they are related to the basic stair geometry. The stair framework of this invention is adaptable to existing manufactured treads. In stair construction for a tall building, the separate spans of the stair flights may be assembled from a col lapsed position on top of each other and then all units extended simultaneously and then attached to the stairwell landings. The stair of this invention can employ closed or open risers as desired. The stair embodiments of this invention will readily adapt to any landing condition and will even adapt to an odd or an even number of treads or risers or one-half treads or one-half riser connection conditions at landings. Each stair can be constructed of several materials each with a variety of attractive finishes.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A through ID are views of the members em ployed within the first embodiment of this invention without the stringers;

FIG. 2 is an elevation side view of the first embodiment indicating the member relationships with a phantom view where the rise is a minimum;

FIG. 3 is a schematic diagram to show clearly the adjusting movement of the first embodiment with numbered points relate to member parts in FIG. 2;

FIG. 4 is a cross-sectional view taken through line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken through line 55 of FIG. 2'.

FIG. 6A is a cross-sectional view of the first embodiment of the stair depicting the tread and riser relationship in the lower position where rise is a maximum;

FIG. 6B depicts the upper position where the rise is a minimum;

FIG. 7A is an elevation of a number of consecutive flights;

FIGS. 78 through 7M are diagrammatical views of twelve different stair framework configurations:

FIG. 8 is a side elevation view of the first embodiment which has been designed to be adapted to the forming of a concrete stair;

FIG. 9 is a cross-sectional view taken through line 99 of FIG. 8;

FIG. 10 is a cross-sectional view taken through line 10-10 of FIG. 8;

FIG. 11 is a side view of a finished concrete stair that has been formed using the structure of FIG. 8;

FIG. 12 is a crosssectional view of the first embodiment framework prior to pouring concrete;

FIG. 13 is a cross-sectional view through line l3 [3 of FIG. 12;

FIG. 14 is a phantom view of FIG. 13 to depict the upper position where the rise is a minimum;

FIG. I5 is a cross-sectional view similar to FIG. 12 after the cement has been poured;

FIG. 16 is a side elevational view of the second em bodiment indicating the member relationships with a phantom view where rise is a minimum;

FIGS. 17A through 17C are views of the members employed within the second embodiment of this invention without the stringers;

FIG. 18 is a schematic diagram to show clearly the adjusting movement of the second embodiment with the numbered points relating to the member parts in FIG. 16',

FIG. 19 is a cross-sectional view taken through line 19l9 of FIG. 16;

FIG. 20 is a cross sectional view of a tread and riser to show relationships at the extremes of adjustment;

FIG. 2l is a side elevational view of the third embodiment indicating the member relationships with a phantom view where rise is a minimum;

FIGS. 22A through 22C are views of the members employed within the third embodiment of this invention without the stringers;

FIG. 23 is a schematic diagram showing clearly the adjusting movement of the third embodiment with the numbered parts relating to the member parts of FIG. 21;

FIG. 24 is a cross-sectional view taken through line 24-24 of FIG. 21; and

FIG. 25 is a cross-sectional view taken through line 25-25 of FIG. 21 to show stair supported on a wall along one side as a variation not heretofore shown.

DETAILED DESCRIPTION OF THE SHOWN EMBODIMENTS Referring in particular to FIGS. 1 through 6 of the drawings, there is shown the first embodiment 20 of this stair invention shown basically composed of three different treads 22, 24 and 26. Each step is composed basically of a pair of tread carriers 28, a tread and a pair of vertical tread spacers 44 which may be attached to a closed riser pan 32. The closed riser 32 may be eliminated if desired to achieve an open area between adjacent treads. Although there are only three treads shown in the drawings, it is to be understood that top tread 22 occurs at the top landing connection and the bottom tread 26 occurs at the bottom landing connection. The middle tread 24 occurs any number of repeated times between 22 and 26. However. 22, 24 and 26 may be identical and could be composed of the same number of parts.

The tread carriers 28 are opposed, one on either side and each comprise a flat metal link placed on edge. The tread carrier 28 will always be positioned horizontally.

Two tread carriers 28 support the tread 30. The tread 30 will normally be formed of a sheet metal material. The tread 30 can be made integral with the tread carriers 28 as shown in tread 24 of FIG. 25 of the drawings. Tread 30', FIG. 2 and FIG. 5 show a cast metal tread.

Adjacent to the front of each of the tread carriers 28 is formed therein a horizontally elongated slot 34. At the back of each of the tread carriers 28 is a hole 36. The function of 34 and 36 will be explained further on in the specification.

Located on each side of the stair is a pair of upper stringers 38 and lower stringers 40 which are identical to each other and are comprised of elongated flat rigid members, usually formed out of metal, and include a plurality of holes 42 formed therein equally spaced apart. The stringers 38 and 40 on both sides of the stair are positioned in a parallel relationship and spaced several inches apart.

lnterconnecting each of the stringers 38 and 40 are a plurality of vertical tread spacers 44. Within this first embodiment 20, the vertical tread spacers 44 are constantly maintained in a vertical relationship during the adjustment movement. Each of the vertical tread spacers are formed in the shape of a flat rigid link and include hole 46 adjacent to one end and an elongated vertical slot 48 at the other end.

Also, interconnecting the stringers 38 and 40 on each side of the first embodiment 20 are a plurality of inclined stringer spacers 50. The minimum number of inclined stringer spacers per side are two in number but there may be be several employed. The distance between the holes in the inclined stringer spacers 50 is selected to be one half the distance between the holes 42 in stringers 38 and 40, to create a right angle relationship between the vertical tread spacer 44 and its particular tread carrier 28. This right angle relationship never changes within the first embodiment of this invention during the entire range of adjustment. For reasons of landing attachment and appearance, such a relationship is desirable.

Located within the inclined stringer spacer 50 adjacent to each of the ends are holes 52. The connecting together of the inclined stringer spacers, the vertical tread spacers, the stringers, the tread carriers and the treads may be accomplished by means of conventional bolts 54 and nuts 56. The use of the bolts 54 and nuts 56, when slightly loosened, permit the adjustment movement of the first embodiment of this invention between the solid line position and the phantom line position shown in FIG. 2. Once the desired position is obtained, the bolts and nuts are then tightened to fix that position. The bolts 54 are conducted through holes 52 of the stringer 38 or 40 and then through the appropriate aligned aperture within the tread carrier which could either be hole 36 or slot 34. If the inclined stringer spacer comes up against a vertical tread spacer 44, the bolt will also be passed through the appropriate hole 46 or slot 48. As a result, the first embodiment 20 ofthis invention is assembled basically as shown in FIG. 2.

The vertical tread spacers 44 as well as the tread carriers 28 may be reversed and the same movement will result. This type of arrangement is shown in FIG. 2 wherein one of the vertical tread spacers 44 is reversed with respect to the remaining tread spacers (this is shown by the slot 48 being located adjacent the lower stringer 40 wherein the other slots 48 are located adjacent the upper stringer 38).

In the assembling of the different parts. any assemblage procedure may be chosen to produce the desired relationship. For example, the different parts can be arranged side by side as shown in the examples of FIG. 4 and FIG. 5. It is considered to be within the scope of this invention that the parts can be arranged in any par ticular desired manner. Normally, it is preferred that the parts be arranged per the particular installation. and, it is desirable to arrange the parts to achieve maximum strength qualities and ease of erection.

Referring in particular to FIG. 2, the same adjustment movement for treads 22, 24 and 26 are depicted. For purposes of the illustration let it be assumed that tread 22 is depicted with the bolt 55 cooperating with slot 48 and fixed to a landing. The maximum rise position is shown in solid lines in FIG. 2 with the minimum rise re-adjusted position shown in phantom lines in FIG. 2.

As the stair is manually moved from the lower position to the upper position, the bolt 55, instead of resting against the upper side of the slot 48, will come in contact with the lower side of the slot 48. Also, the bolt 54 in cooperation with slot 34, will move from the rear side of the slot 34 to the front side of the slot 34. Referring to FIG. 3, it is to be noted that the connection of the inclined stringer spacer 50 to the stringer 38 is at the center point of a circle passing through the center point of the remaining bolts 54 for that particular step. One bolt 54 cooperates with slot 48 with another bolt 54 cooperating with slot 34 and still another bolt 54 00- operates with hole 36. The resulting movement produces a vertical movement denoted v and a horizontal movement denoted h and .T i v can b made to coop. erate in a selected proportion 'atio. The movement of each succeeding step is accum lzui so as a lt, the second step 24, moves 2h and L\ the third step 26 moves 3h and 3v. The values for h ana u may be only a matter of an eighth of an inch or three-sixteenths of an inch as it is desired to keep the length of th slot 48 and 34 as small as possible so that when the bolts 54 are fastened, the slots can be concealed from view. However, because the adjustment is accumulative throughout the total run of the stair, the end of the stairway will be moving as much as several inches in the horizontal direction h, but the vertical direction v can be proportioned greater to exceed the horizontal movement. For example, h can be selected equal to two-thirds v which is a desirable mathematical proportion As the adjust ment proceeds from the lower position to he upper position, the net run of the tread is increased and the tread nosing decreases permitting the movement of the bolts within the provided apertures. It the movement is reversed, the opposite movement results.

The normal stairway comfort relationship that is preferred is that as the run is increased the rise should be decreased proportionally and vice versa. So, therefore,

the stair of this imention inherently achieves a preferred proportion ratio between the run and rise. A tread with a 1% inch slot equal to v with a three-fourth inch slot in the tread carrier equal to It would allow a 3 inch variance in rise selection without \iolating this ratio. The most preferred value and common comfort role is for the rise plus run to equal betvtecn l7 inches and 18 inches. FIG. 3 schematic is scaled to indicate an ideal rise of Tie inches and a run of ill inches. or I7 inches following the comfort rule. These measurements established 11 t\vothirds v. By way ot'examplc. an l l inch mistake in measurmg the total rise in an average flight. can be compensated for by as little as one-eighth inch in slot 48.

The first embodiment of stair of this invention may be prefabricated, prior to transportation to the job site for erection, or the stair can also be shipped to the job site partially assembled or in a collapsed condition The stair designed for the rise and span (or run) between landings automatically establishes the known physical dimensions in space for connecting it at the landings. It is common that there will be small dimensional errors between the space provided for the stair and the space the stair will occupy in the erected position. These errors can readily be compensated for by fixing either the top or the bottom end of the stair to its respective landing and then moving the other end of the stairway into connection with its respective landing.

The primary feature of the self-adjusting stair invention is that the stair cooperates with any conventional landing or column that has a bolt or pin connection. An example of a significant number of landing conditions is shown in FIG. 7A. The numbers 1 through 6 each refer to a landing. Between landings 3 and 4 is a riser which divides the landing into two levels thereby reducing the total run and number of treads between landings 2 and 5. The dash lines indicate how the same additional stair parts maybe used with columns to extend the framework between successive flights. This will create a self-supporting system of flights which does not necessarily rely on the support provided by the conven tional stairwell shaft. FIGS. 7A and 78 through 7M illustrates the stair parts arranged in a plurality of different ways to show the different configurations that are possible without invalidating the adjustment move ment. Each configuration utilizes the geometry of the adjustment movement. The pin connections only at landings are shown and the slots (which are the slide means) are indicated.

A feature of the framework of this invention is that balusters which are used to connect and to support handrails, can also be an integral extension of the framework parts as shown in dotted lines. As shown particularly in FIG. 2, the vertical tread spacers may be extended in an upward direction to connect with a handrail (not shown} which will parallel the upper stringer and supports such. Therefore, balusters can be incorporated and prefabricated along with the stair of this invention.

Previously. there has been difficulty in erecting forms or removing the forms of concrete Stairways. The normal procedure is time consuming relating to the construction of the forms and the critical placement of the reinforc ng steel.

Referring particularly to FIGS. 8 through I] of the drawings. there is shown a modification of the first em bodiment 20 which is to facilitate the pouring of a concrcte stair. Within FIG. 8, a concrete stairway pouring form framework 58 is shown which is to be adjustable in the same manner as the first embodiment 20. The form 58 includes a vertical tread spacer 60 and string ers 38. 62 and 40. inclined stringer spacers S0 and 66, and tread carriers 28. The elements of the form 58 are arranged in exactly the same way as in the first embodiment 20. The form 58 is intstulled at the location where the concrete stairway is to be formed. The form is adjusted to fit the exact dimensions of the particular location in the same manner as the first embodiment 20 was adjusted. A plurality of spaced apart slots are formed along each vertical tread spacer. A transverse threaded rod snap'tie with cones at the ends are to be positioned at selected locations between each side of the form 58 within an opposed number of aligned slots 70 or any other desirable hole or slot locations. Longitudinal reinforcing bars 74 may then be accurately positioned in respect to the transverse rods 72 and wiretied as is the custom. Because of the aperture 70 locations, the reinforcing steel (bars 72 and 74] will remain in the precise desired position during the pouring of the concrete.

Within the form 58, a variety of riser pans can be employed. For example. a vertical riser pan 32 can be employed which establishes a right angle relationship between the riser and the tread. The pan 32 is placed in position between the top stringer guide 62 and the tread carrier 28 and is to function to prevent the concrete from flowing forwardly of the pan 32. By using the pan 32, the riser of tread 78 of FIG. 11 will be formed. The riser pan 32 will remain in position. The riser pan 32 is of deformed sheet metal of various protiles. as shown by cross section of four variations in steps of FIGS. l2, l4 and 15.

If preferred, tread 80, FIGS. 8 and 11, may be formed which employs a cast-in expanded metal mesh screen a short distance from the riser finished surface of an inset riser. This screen 82 retains large aggregate but lets the sand and cement bleed through for easy hand finishing, or may be left as a hardened substrate for decorative cementous coatings applied later. Tread 84 is formed like tread except that its nosing 85 is detached from screen 82 and is connected to tread carrier 28.

Once the cement is poured within the form 58, the concrete is then permitted to harden sufficiently to per mit removal of the form 58 for reuse. The thickness of the stair is determined by the plywood soffit 86 position which is held in place by resting upon steel bars 88 which are resting within aligned slots 70 within different vertical tread spacers 60 as desired. By varying the position of the plywood soffit 86, the strength of the poured concrete stairway 90 is controlled. Cross section detail is seen in FIG. 9 to illustrated wood form 57, poured cement 59 and relationship of the stair member parts.

After the cement has hardened sufficiently to remove the form 58. the workmen knock-out the bars 88 permitting the soffit 86 to separate easily from the rest of the framework of 58. Also. form 58 may be attached to the conventional landing formwork at 92 or 94 to be removed later along with the landing formwork. After the form 58 is removed. the cone forms at the ends of 72 which are exposed and flush with the sides are removed and rod 72 is snapped off at the bottom of the cone hole recess from the side. The hole may be left unfinished or may be filled with cement. Balusters 96 may be attached by bolts to the sides of the stair 90 by the use of a cast-in metal insert with female threads 75 to permit the connection to a handrail.

Concrete stair 90 using form 58 of this invention will be assured of having identical treads and risers throughout the total span of the stair. The concrete stairway 90 is formed precisely to the specific landing conditions at the construction site. Also. the form 58 is easily installed with guides to accurately place reinforcing bars without the need of bar supports resting on the forms. Once the concrete has hardened sufficiently. the form 58 can be quickly removed to be reused.

Reference FIGS. l2. l3 and 14, additional utility of the stair invention in connection with concrete. Member parts 28, 32. 40. S and 66. which can be arranged so that these parts can also serve as a guide and be left cast into the concrete for extra strength and convenience. The riser pans 32 are shown in four sample configurations to meet esthetic or functional requirements. This configuration is particularly amenable to casting on grade. However. it also can use the soffit form 86. In this application the upper stringer is not used. FIG. is a cross-section of FIG. 12 after the cement has been poured. FIG. 14 illustrates a riser detail 32 in the upper position where the rise is a minimum. These riser pans can be left or removed for reuse as desired.

Embodiments two and three of this invention, which are now to be described, employ one less part in that there is no inclined stringer spacer 50 required. The second and third embodiments of this invention should be easier and less expensive to manufacture than the first embodiment. However. the first embodiment. in all probability, would be preferable to customers in most instances due to the constantly maintained right angle relationship established between riser and tread and the complexities of landing attachments. The first embodiment has an extra facility to create a selfsupporting framework without the support of surrounding construction.

It is to be understood that each of the pin connections established between the parts within each of the embodiments of this invention permits movement of the other parts with respect to the pin or bolt. This movement results in substantially the same adjusting movement for each embodiment.

The second embodiment 98 is shown in FIGS. 16 to 20 of the drawings. The second embodiment 98 ineludes tread carriers I00. tread spacers 102. and upper stringers 38 and lower stringers 41). Each of the mem bers, FIG. 18, of the second embodiment 98 are connccted together by bolts 54 to establish the desirable pivotal connection between the parts and thc adjustment is essentially identical to the first embodiment 20.

By referring in particular to FIG. 20, the tread carriers 100 are to support a tread 110. The tread 110 can be formed of a flat sheet metal material alone or inverted and filled with cement later as shown in FIG. 19.

Each of the tread carriers include an elongated hori zontal slot 112 on one end. The slot 112 permits the ad justment movement of the second embodiment 98 of this invention from the solid line position shown in FIGS. 16 or 20 to the phantom line position also shown in FIGS. 16 and 20. The upper and lower ends of the second embodiment 98 are fixed to a landing 92 by means ofa bolt 55. The second embodiment 98 is permitted to pivot about bolt 55 at the upper end during 10 the adjustment procedure. The second embodiment 98, FIG. I6. shows three steps 22. 24 and 26.

The tread spacers 102 assumes a vertical position when tread rise is at maximum position. but at all other adjustment positions are gradually inclined. The second embodiment of this invention for certain types of installations. is preferable to the first or third embodiments. The previously enumerated advantages applies to the second embodiment 98 of this invention, as well as to the first embodiment.

The third embodiment 124 of this invention is shown in FlGS. 2] through 25 of the drawings. The third embodiment 124 includes tread carriers [01. tread 101'. tread spacer 44. upper stringer 38 and lower stringer 40. Each of the members of FIG. 21 and FIG. 23 of the third embodiment 124 are connected together by bolts 54 to establish the desired pivotal connection between the parts and the adjustments is essentially identical to the first embodiment 20.

The distinctiveness of the third embodiment when compared to the second embodiment is that the horizontal, elongated slots 112, which were formed in the tread carriers for adjustment movement are not employed in the third embodiment 124. Instead, there is a vertical elongated slot 48 formed in each vertical tread spacer 44. The slot 48 permits adjustment in a manner similar to the adjustment in the second embodiment. The adjustment for each tread is depicted in the diagram of FIG. 23. Again, like the second embodiment 98, the vertical tread spacers 44 will be gradually inclined until the rise is maximum when the adjustment is moved away from the lower position of the adjustment movement. When in the lower position of movement, like the second embodiment 98, the tread spacers 44 are vertical.

However. it is to be noted that, although the tread spacers 44 will be inclined throughout most of the adjustment range. the amount ofgradual inclination is significantly less in the third embodiment 124 than the second embodiment 98, which is a desirable advantage for landing attachment.

As is shown in section 24, the tread spacers 44 with slot 48 adjacent to lower stringer 40, may be reversed as shown in section 25 with slot 48 adjacent to upper stringer 38.

A baluster 128 may be employed in combination with the third embodiment 124 with the end of the baluster connected at the bottom by a bolt 130 to a tread carrier 101. The baluster is also field connected by a bolt [32 to the upper stringer after the baluster is made plumb.

By referring in particular to FIGS. 24 and 25 of the drawings. it can be seen that the treads can take many configurations. The use of wood. cement and other types of rigid treads may be shown to be employed. Also. it is to be noted that the tread carriers 101 could assume any of the different configurations shown in FIGS. 24 and 25.

What is claimed is:

l. A self-adjusting stair framework formed of a plurality of interconnected linkage members, said framework comprising:

a plurality of treads positionable in a substantially horizontal relationship, each of said treads having a front side and a rear side and a pair of lateral sides, each of said treads supported by a pair of tread carriers, a said tread carrier located at each said lateral side of each of said treads;

a pair of upper stringers. each said upper stringer pivotally connected to said tread carriers:

a pair of lower stringerseach said lower stringer pivotally connected to said tread carriers;

a vertical tread spacer located between and pivotally connected to each adjacent pair of said treads; and

at least one longitudinal slot means formed within one of said linkage members said slot means located at the pivotal interconnection between a pair of said members. said slot means permitting adjustment of said framework between a minimum rise adjustment position and a maximum rise adjust ment position, said maximum adjustment position being displaced horizontally and vertically from said minimum adjustment position throughout the adjusting movement.

2. The framework as defined in claim 1 wherein:

during said adjusting movement the amount of said horizontal movement is equal to two-thirds of the amount of said vertical movement.

3. The framework as defined in claim 1 wherein:

therebeing a said upper stringer and a said lower stringer located on each said lateral side of said treads, on each said lateral side said upper stringer being parallel with said lower stringer.

4. The framework as defined in claim 3 wherein: each of said upper stringers being parallel and in transverse alignment with respect to each other.

5. The framework as defined in claim 4 wherein:

each said lower stringers being parallel and in transverse alignment with respect to each other.

6. The framework as defined in claim 5 wherein:

each said upper stringer pivotally connected to said tread carriers adjacent said front side of said treads, each of said lower stringers pivotally connccted to said rear side of said treads.

7. The framework as defined in claim I wherein: said longitudinal slot means includes a slot horizontally located within each of said thread carriers.

8. The framework as defined in claim 7 wherein:

said slot means further includes a second longitudinal slot. said second longitudinal slot being vertically disposed within each said tread spacers.

9. The framework as defined in claim 8 further ineluding:

an inclined tread spacer assembly, said inclined tread spacer assembly comprising at least a pair of links pivotally connected between said upper and lower stringers on each lateral side of said framework. the length and selection of interconnection points being such that said vertical tread spacers are fixed in a right angle relationship with respect to said treads.

10. The framework as defined in claim 1 wherein:

said slot means includes a single longitudinal slot formed within each of said tread spacers 11. The framework as defined in claim 10 wherein:

said slot means includes a second longitudinal slot, said second longitudinal slot located within each of said tread carriers.

12. The framework as defined in claim 11 wherein:

an inclined tread spacer assembly comprising at least a pair of links pivotally connected between said upper and lower stringer on each lateral side of said framework. the length and selection of interconnection points being such that said vertical tread spacers are fixed in a right angle relationship with respect to said treads. 

1. A self-adjusting stair framework formed of a plurality of interconnected linkage members, said framework comprising: a plurality of treads positionable in a substantially horizontal relationship, each of said treads havIng a front side and a rear side and a pair of lateral sides, each of said treads supported by a pair of tread carriers, a said tread carrier located at each said lateral side of each of said treads; a pair of upper stringers, each said upper stringer pivotally connected to said tread carriers; a pair of lower stringers, each said lower stringer pivotally connected to said tread carriers; a vertical tread spacer located between and pivotally connected to each adjacent pair of said treads; and at least one longitudinal slot means formed within one of said linkage members, said slot means located at the pivotal interconnection between a pair of said members, said slot means permitting adjustment of said framework between a minimum rise adjustment position and a maximum rise adjustment position, said maximum adjustment position being displaced horizontally and vertically from said minimum adjustment position throughout the adjusting movement.
 2. The framework as defined in claim 1 wherein: during said adjusting movement the amount of said horizontal movement is equal to two-thirds of the amount of said vertical movement.
 3. The framework as defined in claim 1 wherein: therebeing a said upper stringer and a said lower stringer located on each said lateral side of said treads, on each said lateral side said upper stringer being parallel with said lower stringer.
 4. The framework as defined in claim 3 wherein: each of said upper stringers being parallel and in transverse alignment with respect to each other.
 5. The framework as defined in claim 4 wherein: each said lower stringers being parallel and in transverse alignment with respect to each other.
 6. The framework as defined in claim 5 wherein: each said upper stringer pivotally connected to said tread carriers adjacent said front side of said treads, each of said lower stringers pivotally connected to said rear side of said treads.
 7. The framework as defined in claim 1 wherein: said longitudinal slot means includes a slot horizontally located within each of said thread carriers.
 8. The framework as defined in claim 7 wherein: said slot means further includes a second longitudinal slot, said second longitudinal slot being vertically disposed within each said tread spacers.
 9. The framework as defined in claim 8 further including: an inclined tread spacer assembly, said inclined tread spacer assembly comprising at least a pair of links pivotally connected between said upper and lower stringers on each lateral side of said framework, the length and selection of interconnection points being such that said vertical tread spacers are fixed in a right angle relationship with respect to said treads.
 10. The framework as defined in claim 1 wherein: said slot means includes a single longitudinal slot formed within each of said tread spacers.
 11. The framework as defined in claim 10 wherein: said slot means includes a second longitudinal slot, said second longitudinal slot located within each of said tread carriers.
 12. The framework as defined in claim 11 wherein: an inclined tread spacer assembly comprising at least a pair of links pivotally connected between said upper and lower stringer on each lateral side of said framework, the length and selection of interconnection points being such that said vertical tread spacers are fixed in a right angle relationship with respect to said treads. 